Brush bristles having a reduced fracturable transverse axis



April 18, 1950 F. HENLEY BRUSH BR LES HAVING A REDUCED FRACTURAB TRVERSE AXIS File ov. 1945 ATTO RNEY Patented Apr. 18, 1950 BRUSH BRISTLESHAVING A REDUCED FRACTURABLE TRAN SVERSE AXIS Charles Frederick Henley,London, England, as-

signor to American Safety Brooklyn,

Razor Corporation,

N. Y., a corporation of Virginia Application November 2, 1945, SerialNo. 626,355

2 Claims.

This invention relates in one aspect to brush bristles and in another totheir production from synthetically extruded filaments of indefinitelength.

Some of the general objects of my invention are: the provision of abrush bristle whose end will .tend to split into outwardly flaggingsections when the brush is applied to a surface; the provision of abrush bristle which is readily fracturable in the direction of itslength by sharply diminishing its cross-section along a diameterthereof; the provision of a brush bristle comprised of longitudinallyextending lobes connected in lateral relation by a longitudinallyextending neck to define a line of fracture; and the provision of abristle of the character referred whose cross-section is generallykidney shaped.

Other general objects of my invention are: the provision of asynthetically formed filament of indefinite length and whosecross-section is such that the end of a brush bristle length cuttherefrom will tend to split into outwardly fiagging sections whenapplied to a surface in a normal brushing or painting operation; theprovision for this purpose of a filament whose thickness is reduced fora portion of its cross-section and more particularly whose cross-sectionis kidney shaped; and the provision of a procedure and apparatus wherebythe aforementioned cross-section is given the filament simultaneouslywith its formation.

Synthetic filaments are formed of indefinite length by extruding aplastic mass through openings in a die and generally then passing thealready formed filaments under tension through smaller sized openings ina second die spaced from the first to thereby reduce the thickness ofthe filaments. This procedure is shown diagrammatically in theaccompanying drawings and will be referred to hereinafter by referenceto this showing.

I attain the second group of general objects by the use of openings inthe first mentioned die which shapes each filament so that it is readilyfracturable along its length. In the disclosed embodiment the filamentsare each shaped to define lobes or threads connected by a neck ofreduced thickness and along which the filaments of reduced lengthsthereof are weakened lengthwise thereof and more specifically filamentswhose cross-sections are generally kidney shaped. Where the overallthickness of the filament is reduced by passing it, after its extrusion,through smaller openings, the attainment of my scale;

Fig. 2 is a front elevational view, partly broken away, of the bristleof Fig. 1 drawn on a smaller scale, showing the outwardly flagging splitlower end;

Fig. 3 is a diagrammatic showing of an extrusion die for forming thefilament;

Fig. 4 shows diagrammatically a means which may be employed formaintaining the contour of the filament while its thickness is beingreduced; and

Fig. 5 is a section taken on line 55 of Fig. 4 looking in the directionof the arrows.

Before proceeding to describe the details of the disclosed embodimentand of its production, I will premise that the ultimate object of myinvention is a synthetic brush bristle which initially is integralthroughout but which will readily fracture lengthwise of that endthereof which is applied to a surface during the brushing or paintingoperation and that it is an ancillary object of my invention that thisbrush bristle be produced simultaneously with and by the apparatusgenerally employed in the production of synthetic filaments, which Iwill now briefly describe by reference to Figs. 3, 4, and 5 of thedrawings.

The element Hi in Fig. 4 is intended as a diagrammatic showing of theextrusion die having openings ll through which the mass is extruded toform synthetic filaments of continuous length. In general practice, thedimensions of these openings l l are uniform, e. g., circular. Thefilaments extruded through the openings II are then led under tension tothe openings l3 in a second die member l2, positioned at a distance fromthe first mentioned die member I 0. The openings l3 are shaped like theopenings I i but are much smaller than the openings l. The purpose ofthis operation is to compact or reduce the thickness of the filament.

I avail myself of this procedure and arrangement to the followingextent. The openings H through which the mass is initially extruded andwhich as stated has a regular cross-section to form a filament ofuniform thickness is given a crosssection wherein the intermediateportion of the opening is narrower than the portions to the side thereofso that a filament extruded through such opening will be caused to takethat conformation and therefore to have its intermediate portionlengthwise thereof. of reduced thickness and therefore weakened to thatextent and my invention contemplates that this weakening be effected ina manner and to a degree and for the purpose shortly to be pointed out.This may be effected in various ways. One specific way is shown in Fig.3 wherein the opening in the extrusion die i is shaped as shown at II inFig. 3. This opening can be described as kidney shaped or as resemblingthe number 8 and will shape the filament correspondingly so that it iscomprised of two laterally related lobes demarked or defined bydepressions oppositely and centrally thereof.

While Fig. 1 is intended to illustrate a finished bristle in accordancewith my invention. it can also be considered as a section of thefilament produced by the die of Fig. 3 because the brush bristle is cutfrom the filament so formed. In Fig. l the brush bristle (or thefilament) is shown as having the appearance of twin threads 15 and I6which are joined or fused into each other to leave the opposeddepressions l1 and I8 which define a narrow neck portion in between thetwo lobes l and IS. The thickness of this neck portion is much less thanthat of the bristle portions (5 and IE to each side thereof. Thisreduced thickness is shown at a-a in this figure. The reduced openings[3 in the reducing die l2 conform generally to the contour of theopenings ll) of the extrusion die, except that their dimensions aresubstantially and proportionately reduced. This can be seen by comparingthe size of the openings II and I3 in Fig. 4.

One of the problems which presented itself in using procedures hithertoemployed in forming synthetic filaments was the fact that the extrudedfilaments were led under tension into and through the reduced openingsl3 and the shape and conformation given them by the openings II in theextrusion die were altered by the tension imposed upon the filament asit was led to and through the reducing opening I3. I have thereforeprovided the opposed shape retaining members 20 and 2| shown in Fig. 4partly in side elevation and partly broken away and shown incross-section in Fig. 5. These shaping members 20 and 2i comprise curvedsurfaces 22 and 23 which intersect at the apex 24. These curved surfacesare predeterminately conformd so that at their right end they aredimensioned to seat into the depressions l1 and 18 of the initiallyextruded filament and which dimensions diminish gradually to those ofthe corresponding portions of the opening l3 and for which purpose theapex 24 and the faces 22 and 23 all converge as shown in Fig. 4approximately and to the extent that the dimensions of the filament arereduced in its passage to and through the openings l3. The charactercontours and dimensions of these shape retaining members are controlledby the shape which it is desired the bristle shall have and the specificcharacteristics shown and described are built around the specificshowing of Fig. 1.

The showings in the drawings are entirely diagrammatic and theproportionings are not intended to represent either actually orapproximately the proportions actually employed in practice. In

the general practice of forming conventional filaments, the initiallyextruded filament may have a diameter of the order of from .016" to.056" and is reduced in diameter in the proportion of 3 or 4 to 1, sothat in the aforementioned order of range the diameter of the filamentextruded through the opening l3 will range between .004" to .014". Inthe finished product of Fig. 1, which, as stated, may be construedeither as a section of the filamentor as a completed brush bristle, thediameter of the lobes can therefore be assumed to be within the range ofreduced diameters of .004 to .014 so that the filament or bristle alongits longest dimension would be approximately twice that length whereasthe distance across its shortest dimension along the line (1-0 may be aslow as .001 to .0015.

It will be understood that these dimensions are merely exemplary and aregiven as stated because they are in line with the present practice inmanufacturing a conventional synthetic fila merit.

Fig. 2 is intended to show the manner of functioning of a bristle of thespecific character which has herein been disclosed for purposes ofexemplification. The lower end is presumed to have been applied to asurface in the normal operation of painting and to have split into thesections 30 and 3| which are automatically flagged outwardly. Thismaterially increases the capacity of the bristle to handle paint andalso its flexibility and presents other advantages which will beunderstood by those skilled in the art. As the split end sections 30 and3| wear away and new end portions are brought against the surface in thepainting operation, the splitting will be continued upwardly so that thebristle end will gradually split automatically along its length intooutwardly flagging sections with wear.

The specific embodiment shows a bristle whose cross-section is contouredsymmetrically with ref erence to both its long and short axes so as todefine two similar lobes and give the appearance of a twin threadconstruction. It will be understood that the attainment of all theobjects of my invention does not require that the contour of thecross-section be symmetrical or that it be kidney shaped or that thediminishment of the thickness of the intermediate portion be such as todefine lobes or that where it does define lobes that their number berestricted to two.

It will also be pointed out that my invention does not require that thetwin threads be each contoured cylindrically.

What I claim as new and desire to secure by Letters Patent is:

1. A synthetic bristle adapted for use in a paint brush presenting theends of a plurality of held bristles to the surface to be painted, thecross section of said bristle having a major longitudinal axis and aminor transverse axis, and an outline which is symmetrical with respectto both said axes, said bristle having its maximum transverse dimensionat points equi-distanced from said minor axis and a substantiallyreduced transverse dimension at said minor axis, said transversedimension at the minor axis being sufiiciently small to result infracture of the bristle at its said minor axis to present twosymmetrical flagged portions at the bristle end, the remainder of thebristle remaining integrally united at the minor axis, action of thebrush against said surface causing said flagging fracture of thebristle, said flagging action being uniformly progressive along thelength of the bristle as the end thereof become; worn.

2. A synthetic bristle adapted for use in a paint brush presenting theends of a plurality of held bristles to the surface to be painted, thecross section of said bristle having a major longitudinal axis and aminor transverse axis, and having its maximum transverse dimension atpoints equidistanced from said minor axis and a. substantially reducedtransverse dimension at said minor axis, said transverse dimension atthe minor axis being suniciently small to result in fracture of thebristle at its said minor axis to present two flagged portions at thebristle end, the remainder of the bristle remaining integrally united atthe minor axis, action of the brush against said surface causing saidfla ging fracture of the bristle, said flagging action being uniformlyprogressive along the length of the bristle as the end thereof becomesworn.

CHARLES FREDERICK HENLEY.

8 nnrnnnncns man The following references are of record in the file ofthis patent:

UN ITED STATES PATENTS Number Name Date 1,944,378 'I'henoz Jan. 23, 19342,099,030 Morrison Nov. 16, 1937 2,129,213 Harz Sept. 6, 1939 l02,207,156 Neville et a1. July 9, 1940 2,227,126 Cooke Dec. 31, 19402,313,296 Lamesch Mar. 9, 1943 2,341,823 Smith Feb. 15, 1940 2,366,495DAlelio Jan. 2, 1945 15 2,373,892 Hickey 'Apr. 17, 1945 2,387,791Hoifman Oct. 30, 1945 2,433,325 Slaughter Dec. 23, 1947 2,443,055 ReisJune 8, 1948 o FOREIGN PATEWTS Number Country Date 840,347 France Apr.24, 1939

